In one type of optical mouse, the optical mouse uses photodetectors arranged as an image array of pixels to image the spatial features of generally any micro textured or micro detailed work surface located below the optical mouse. Photodetector responses are digitized and stored as a frame into memory. Motion produces successive frames of translated patterns of pixel information. The successive frames are compared by cross-correlation to ascertain the direction and amount of movement. For more information on this type of optical mouse, see, for example, U.S. Pat. No. 6,281,882 B1.
The imaging and performance tracking required by optical mice, and similar pointing devices that require optical navigation sensing, rely heavily on uniform illumination across the array of pixels. Uniform illumination is obtained by careful alignment of the array of pixels, an illuminator and accompanying optics. Such careful alignment can be expensive from a manufacturing point of view.